Photocurable compositions with alicyclic epoxides of high monomer purity

ABSTRACT

The present invention relates to novel resin compositions containing at least one solid or liquid actinic radiation-curable and cationically polymerizable organic substance, an actinic radiation-sensitive initiator for cationic polymerization, an actinic radiation-curable and radical-polymerizable organic substance and an actinic radiation-sensitive initiator for radical polymerization. The actinic radiation-curable and cationically polymerizable organic substance is at least one glycidylether of a polyhydric aliphatic, alicyclic or aromatic alcohol having at least three epoxy groups with epoxy equivalent weight between 90 and 800 grams per equivalent, at least one solid or liquid alicyclic epoxide with an epoxy equivalent weight between 90 and 330 grams per equivalent having at least two epoxy groups and monomer purity greater than about 90% by weight, or at least a solid or liquid epoxycresol novolac or epoxyphenol novolac having epoxy equivalent weight between 130 and 350, or mixtures thereof. The use of the above-mentioned cationically polymerizable components substantially increases the heat deflection temperature of the cured articles while maintaining high photospeed, accuracy, wetting-recoatability, water resistance and good side wall finish. The present invention further relates to a method of producing a cured product, particularly a three-dimensional article, in which a compositions described above are treated with actinic radiation.

[0001] The present invention relates to a liquid, radiation-curablecomposition which is particularly suitable for the production ofthree-dimensional shaped articles by means of stereolithography, to aprocess for the production of a cured product and, in particular, forthe stereolithographic production of a three-dimensional shaped articlefrom this composition having a high heat deflection temperature.

BACKGROUND

[0002] The production of three-dimensional articles of complex shape bymeans of stereolithography has been known for a relatively long time. Inthis technique the desired shaped article is built up from a liquid,radiation-curable composition with the aid of a recurring, alternatingsequence of two steps (a) and (b); in step (a), a layer of the liquid,radiation-curable composition, one boundary of which is the surface ofthe composition, is cured with the aid of appropriate radiation,generally radiation produced by a preferably computer-controlled lasersource, within a surface region which corresponds to the desiredcross-sectional area of the shaped article to be formed, at the heightof this layer, and in step (b) the cured layer is covered with a newlayer of the liquid, radiation-curable composition, and the sequence ofsteps (a) and (b) is repeated until a so-called green model of thedesired shape is finished. This green model is, in general, not yetfully cured and must therefore, normally, be subjected to post-curing.

[0003] The mechanical strength of the green model (modulus ofelasticity, fracture strength), also referred to as green strength,constitutes an important property of the green model and is determinedessentially by the nature of the stereolithographic-resin compositionemployed. Other important properties of a stereolithographic-resincomposition include a high sensitivity for the radiation employed in thecourse of curing and a minimum curl factor, permitting high shapedefinition of the green model. In addition, for example, the precuredmaterial layers should be readily wettable by the liquidstereolithographic-resin composition, and of course not only the greenmodel but also the ultimately cured shaped article should have optimummechanical properties.

[0004] Another requirement that has recently become a high priority forstereolithography users is the high temperature performance of curedarticles produced by stereolithography. It is usually measured by theHeat Deflection Temperature (HDT) or Glass Transition Temperature(T_(g)). The HDT value is determined by the ASTM method D648 applying aload of 66 psi.

[0005] For several years, high temperature performance forstereolithography produced articles has been achieved by the use of(meth)acrylate chemistry. This approach primarily entails the use ofvarious commercially available urethane acrylate derivatives. EP-802455of Teijin Seiki Corp. (Oct. 22, 1997) and JP 08323866 of Takemoto Oil &Fat Co Ltd (Dec. 10, 1996) describe acrylate urethane compositions forachieving good heat resistance and strength. However, a majordisadvantage of such acrylate urethane compositions is thatpolymerization is hindered by atmospheric oxygen because polymerizationis of a radical nature, that the cure shrinkage is unacceptably large,that the resins are irritant to the skin, particularly when theviscosity is low (low viscosity is highly preferred forstereolithography applications). Thus, acrylate urethane-basedcompositions show poor practicality for stereolithography.

[0006] Liquid, radiation-curable compositions for stereolithographywhich overcome the abovementioned problems of the acrylate chemistry aredescribed, for example, in U.S. Pat. No. 5,476,748, which is incoporatedherein by reference. These compositions are so-called hybrid systems,comprising free-radically and cationically photopolymerizablecomponents. Such hybrid compositions comprise at least:

[0007] (A) a liquid difunctional or more highly functional epoxy resinor a liquid mixture consisting of difunctional or more highly functionalepoxy resins;

[0008] (B) a cationic photoinitiator or a mixture of cationicphotoinitiators;

[0009] (C) a free-radical photoinitator or a mixture of free-radicalphotoinitiators; and

[0010] (D) at least one liquid poly(meth)acrylate having a(meth)acrylate functionality of more than 2,

[0011] (E) at least one liquid cycloaliphatic or aromatic diacrylate,and

[0012] (F) a certain hydroxy compound that is selected from the groupconsisting of OH-terminated polyethers, polyesters and polyurethanes.Such hybrid systems can optionally further contain vinyl ether-basedresins or other cationically cured components such as oxetanes,spiro-ortho esters.

[0013] A drawback of commercial cationic or hybrid cationic-radicalstereolithographic compositions is that their cured articles show HDTvalues that are much lower than those based on acrylate chemistry,usually between 40 and 100° C.

[0014] Many hybrid compositions have been developed by companies for usein stereolithography process systems. For example, U.S. Pat. No.5,434,196, assigned on its face to Asahi Denka Kogyo K. K., disclosesresin compositions for so-called optical molding containing a mixture ofepoxy resins and vinylethers, a cationic initiator, and a mixture of anacrylate compound and a triacrylate compound.

[0015] To date, there is no scientifically published or universallyaccepted term for defining the high temperature hybrid stereolithographyresins. Through marketing brochures of stereolithography resinmaufacturers and presentations in trade organizations, high temperaturehybrid stereolithography resins are defined as those wherein their curedarticles have HDT values over 80 and about 100° C. The highest HDT valueever reported for commercial hybrid stereolithography resins is about100° C.

[0016] Despite all previous attempts, there exists a need for hybridstereolithography compositions capable of producing high temperatureperformance cured articles for which the photospeed, accuracy, waterresistance are commercially acceptable. Such hybrid compositions shouldpossess HDT values over those of the existing ones, especially over 100°C.

SUMMARY OF THE INVENTION

[0017] The present invention relates to novel resin compositionscontaining at least one solid or liquid actinic radiation-curable andcationically polymerizable organic substance, an actinicradiation-sensitive initiator for cationic polymerization and an actinicradiation-curable and radical-polymerizable organic substance. Thecompositions contain an actinic radiation-sensitive initiator forradical polymerization. The actinic radiation-curable and cationicallypolymerizable organic substance is at least one glycidylether of apolyhydric aliphatic, alicyclic or aromatic alcohol having at leastthree epoxy groups with epoxy equivalent weight between 90 and 700 gramsper equivalent and at least one solid or liquid alicyclic epoxide withan epoxy equivalent weight between 80 and 330 grams per equivalenthaving at least two epoxy groups, or mixtures thereof having a monomerpurity greater than about 80% by weight.

[0018] The composition preferably contains 55-90%, more preferably 20and 75% by weight, of the at least one solid or liquid actinicradiation-curable and cationically polymerizable organic substance, 0.05to 12% by weight an actinic radiation-sensitive initiator for cationicpolymerization, 5% to 25% by weight of an actinic radiation-curable andradical-polymerizable organic substance, and 0.02 to 10% by weight, withthe sum total of components being 100 percent by weight.

[0019] The actinic radiation-curable and cationically polymerizableorganic substance can contain not more than 20% by weight of at leastone liquid or solid vinylether compound having at least twocationically-reactive groups in the molecule or a hydroxy-functionalizedmono(poly)vinylether or mixtures thereof.

[0020] The actinic radiation-curable and cationically polymerizableorganic substance can further contain at least one liquid or solid epoxycresol novolac, epoxy phenol novolac, oxetane or spiro-ortho estercompound having at least two cationically-reactive groups in themolecule, or mixtures thereof.

[0021] The at least one glycidylether of a polyhydric aliphatic,alicyclic or aromatic alcohol having at least three epoxy groups ispreferably between about 3 and 90%, more preferably 15% to 90% by weightof the at least one alicylic epoxide having at least two epoxy groups.

[0022] A further embodiment of the invention is a novel resincomposition containing at least one solid or liquid actinicradiation-curable and cationically polymerizable organic substance, anactinic radiation-sensitive initiator for cationic polymerization, anactinic radiation-curable and radical-polymerizable organic substance;and an actinic radiation-sensitive initiator for radical polymerization.The actinic radiation-curable and cationically polymerizable organicsubstance contains at least one glycidylether of a polyhydric aliphatic,alicyclic or aromatic alcohol having at least three epoxy groups withepoxy equivalent weight between 90 and 700 grams/equivalent and at leastone solid or liquid epoxy cresol novolac, or epoxy phenol novolac withepoxy equivalent weight between about 130 and 350 grams/equivalenthaving at least two functional groups, or mixtures thereof.

[0023] The composition preferably contains between about 55-90% byweight of the at least one solid or liquid actinic radiation-curable andcationically polymerizable organic substance, 0.05 to 12% by weight anactinic radiation-sensitive initiator for cationic polymerization, 5-25%by weight of an actinic radiation-curable and radical-polymerizableorganic substance, and 0.02 to 10% by weight an actinicradiation-sensitive initiator for radical polymerization, with the sumtotal of the components being 100 percent by weight.

[0024] The composition preferably contains the at least one solid orliquid epoxy cresol novolac, epoxy phenol novolac having at least twofunctional groups, or mixtures thereof between 2 and 50% by weight. Theat least one solid or liquid epoxy cresol novolac or epoxy phenolnovolac more preferably has an epoxy functionality at least 3. The atleast one solid or liquid epoxy cresol novolac or epoxy phenol novolacmost preferably has an epoxy functionality at least 4.

[0025] The composition can further include not more than 20% by weightof at least one liquid or solid vinylether compound having at least twocationically-reactive groups the molecule, or a hydroxy-functionalizedmono(poly)vinylether, or mixtures thereof.

[0026] The actinic radiation-curable and cationically polymerizableorganic substance further comprises at least one liquid or solidalicyclic polyfunctional epoxide, oxetane or spiro-ortho ester compoundhaving at least two cationically-reactive groups in the molecule, ormixtures thereof.

[0027] The composition preferably contains the at least oneglycidylether of a polyhydric aliphatic, alicyclic or aromatic alcoholhaving at least three epoxy groups at between 3 and 90%, more preferablyat least 15% to 90% by weight of the at least one solid or liquid epoxycresol novolac, epoxy phenol novolac having at least two functionalgroups.

[0028] The composition can further include about 0.5 to about 40 percentby weight of at least one solid or liquid cationic reactivemodifier-flexibilizer. The at least one solid or liquid cationicreactive modifier is preferably a reactive epoxy modifier or reactivevinylether modifier or a hydroxy-functionalized vinylether or mixturesthereof. More preferably, the reactive modifier-flexibilizer includes atleast one cationically reactive bifunctional aliphatic, alicyclic oraromatic compound containing a chain extension segment connected to thecationic reactive group with a molecular weight of at least about 100and not more than 2000.

[0029] The composition can contain from about 4 to 30% by weight of afree radically curable component comprising at least 4% by weight onemono- or di(meth)acrylate and at least 4% by weight a poly(meth)acrylatehaving (meth)acrylate functionality greater than or equal to 3.

[0030] The present invention further relates to a method of producing acured product, in which a compositions described above are treated withactinic radiation. More preferably, the present invention relates to amethod for producing three-dimensional shaped articles comprising:

[0031] a) treating a radiation-curable composition described above withactinic radiation to form an at least partially cured layer on thesurface of said composition within a surface region corresponding to adesired cross-sectional area of the three-dimensional article to beformed,

[0032] b) covering the at least partially cured layer produced in stepa) with a new layer of said radiation-curable composition, and c)repeating steps a) and b) until an article having the desired shape isformed, and optionally, d) post-curing the resulting article.

DETAILED DESCRIPTION OF THE INVENTION

[0033] The novel compositions herein contain, in the broadest sense, amixture of at least one cationically curable compound and at least onephotoinitator for the cationically cured compound(s), and a selectedfree-radically curable component, wherein the composition preferablycontains substantially no polyol or hydroxyl-group containing compounds.The compositions further optionally contain a free radicalphotoinitiator/sensitizer and a cationic reactive modifier.

[0034] The cationically curable liquid or solid compound mayexpeditiously be an aliphatic, alicyclic or aromatic polyglycidylcompound or cycloaliphatic polyepoxide or epoxy cresol novolac or epoxyphenol novolac compound and which on average possess more than oneepoxide group (oxirane ring) in the molecule. Such resins may have analiphatic, aromatic, cycloaliphatic, araliphatic or heterocyclicstructure; they contain epoxide groups as side groups, or these groupsform part of an alicyclic or heterocyclic ring system. Epoxy resins ofthese types are known in general terms and are commercially available.

[0035] Polyglycidyl esters and poly(β-methylglycidyl) esters are oneexample of suitable epoxy resins. Said polyglycidyl esters can beobtained by reacting a compound having at least two carboxyl groups inthe molecule with epichlorohydrin or glycerol dichlorohydrin orβ-methylepichlorohydrin. The reaction is expediently carried out in thepresence of bases. The compounds having at least two carboxyl groups inthe molecule can in this case be, for example, aliphatic polycarboxylicacids, such as glutaric acid, adipic acid, pimelic acid, suberic acid,azelaic acid, sebacic acid or dimerized or trimerized linoleic acid.Likewise, however, it is also possible to employ cycloaliphaticpolycarboxylic acids, for example tetrahydrophthalic acid,4-methyltetrahydrophthalic acid, hexahydrophthalic acid or4-methylhexahydrophthalic acid. It is also possible to use aromaticpolycarboxylic acids such as, for example, phthalic acid, isophthalicacid, trimellitic acid or pyromellitic acid, or else carboxyl-terminatedadducts, for example of trimellitic acid and polyols, for exampleglycerol or 2,2-bis(4-hydroxycyclohexyl)propane, can be used.

[0036] Polyglycidyl ethers or poly(β-methylglycidyl) ethers can likewisebe used. Said polyglycidyl ethers can be obtained by reacting a compoundhaving at least two free alcoholic hydroxyl groups and/or phenolichydroxyl groups with a suitably substituted epichlorohydrin underalkaline conditions or in the presence of an acidic catalyst followed byalkali treatment. Ethers of this type are derived, for example, fromacyclic alcohols, such as ethylene glycol, diethylene glycol and higherpoly(oxyethylene) glycols, propane-1,2-diol, or poly(oxypropylene)glycols, propane-1,3-diol, butane-1,4-diol, poly(oxytetramethylene)glycols, pentane-1,5-diol, hexane-1,6-diol, hexane-2,4,6-triol,glycerol, 1,1,1-trimethylolpropane, bistrimethylolpropane,pentaerythritol, sorbitol, and from polyepichlorohydrins. Suitableglycidyl ethers can also be obtained, however, from cycloaliphaticalcohols, such as 1,3- or 1,4-dihydroxycyclohexane,bis(4-hydroxycyclo-hexyl)methane, 2,2-bis(4-hydroxycyclohexyl)propane or1,1-bis (hydroxymethyl)cyclohex-3-ene, or they possess aromatic rings,such as N,N-bis (2-hydroxyethyl)aniline orp,p′-bis(2-hydroxyethylamino)diphenylmethane.

[0037] Particularly important representatives of polyglycidyl ethers orpoly(β-methylglycidyl) ethers are based on phenols; either on monocylicphenols, for example on resorcinol or hydroquinone, or on polycyclicphenols, for example on bis(4-hydroxyphenyl)methane (Bisphenol F),2,2-bis (4-hydroxyphenyl)propane (Bisphenol A), or on condensationproducts, obtained under acidic conditions, of phenols or cresols withformaldehyde, such as phenol novolaks and cresol novolaks. Thesecompounds are particularly preferred as epoxy resins for the presentinvention, especially diglycidyl ethers based on Bisphenol A andBisphenol F and mixtures thereof.

[0038] Poly(N-glycidyl) compounds are likewise suitable for the purposesof the present invention and are obtainable, for example, bydehydrochlorination of the reaction products of epichlorohydrin withamines containing at least two amine hydrogen atoms. These amines may,for example, be n-butylamine, aniline, toluidine, m-xylylenediamine,bis(4-aminophenyl)methane or bis (4-methylaminophenyl)methane. However,other examples of poly(N-glycidyl) compounds include N,N′-diglycidylderivatives of cycloalkyleneureas, such as ethyleneurea or1,3-propyleneurea, and N,N′-diglycidyl derivatives of hydantoins, suchas of 5,5-dimethylhydantoin.

[0039] Poly(S-glycidyl) compounds are also suitable as the cationiccuring resin herein, examples being di-S-glycidyl derivatives derivedfrom dithiols, for example ethane-1,2-dithiol or bis(4-mercaptomethylphenyl) ether.

[0040] Examples of epoxide compounds in which the epoxide groups formpart of an alicyclic or heterocyclic ring system includebis(2,3-epoxycyclopentyl) ether, 2,3-epoxycyclopentyl glycidyl ether,1,2-bis(2,3-epoxycyclopentyloxy)ethane, bis(4-hydroxycyclohexyl)methanediglycidyl ether, 2,2-bis(4-hydroxycyclohexyl)propane diglycidyl ether,3,4-epoxycyclohexyl-methyl 3,4-epoxycyclohexanecarboxylate,3,4-epoxy-6-methyl-cyclohexylmethyl3,4-epoxy-6-methylcyclohexanecarboxylate, di(3,4-epoxycyclohexylmethyl)hexanedioate, di (3,4-epoxy-6-methylcyclohexylmethyl) hexanedioate,ethylenebis(3,4-epoxycyclohexane-carboxylate, ethanedioldi(3,4-epoxycyclohexylmethyl) ether, vinylcyclohexene dioxide,dicyclopentadiene diepoxide or2-(3,4-epoxycyclohexyl-5,5-spiro-3,4-epoxy)cyclohexane-1,3-dioxane.

[0041] However, it is also possible to employ epoxy resins in which the1,2-epoxide groups are attached to different heteroatoms or functionalgroups. Examples of these compounds include the N,N,O-triglycidylderivative of 4-aminophenol, the glycidyl ether/glycidyl ester ofsalicylic acid,N-glycidyl-N′-(2-glycidyloxypropyl)-5,5-dimethylhydantoin or2-glycidyloxy-1,3-bis (5,5-dimethyl-1-glycidylhydantoin-3-yl)propane.

[0042] Also conceivable is the use of liquid prereacted adducts of epoxyresins, such as those mentioned above, with hardeners for epoxy resins.It is of course also possible to use liquid mixtures of liquid or solidepoxy resins in the novel compositions.

[0043] Examples of cationically polymerizable organic substances otherthan epoxy resin compounds include oxetane compounds, such astrimethylene oxide, 3,3-dimethyloxetane and 3,3-dichloromethyloxethane,3-ethyl-3-phenoxymethyloxetane, and bis(3-ethyl-3-methyloxy)butane;oxolane compounds, such as tetrahydrofuran and2,3-dimethyl-tetrahydrofuran; cyclic acetal compounds, such as trioxane,1,3-dioxalane and 1,3,6-trioxan cycloctane; cyclic lactone compounds,such as β-propiolactone and ε-caprolactone; thiirane compounds, such asethylene sulfide, 1,2-propylene sulfide and thioepichlorohydrin;thiotane compounds, such as 1,3-propylene sulfide and3,3-dimethylthiothane.

[0044] Vinyl ethers that can be used in stereolithography compositionsinclude ethyl vinylether, n-propyl vinylether, isopropyl vinylether,n-butyl vinylether, isobutyl vinylether, octadecyl vinylether,cyclohexyl vinylether, butanediol divinylether, cyclohexanedimethanoldivinylether, diethyleneglycol divinylether, triethyleneglycoldivinylether, tert-butyl vinylether, tert-amyl vinylether, ethylhexylvinylether, dodecyl vinylether, ethyleneglycol divinylether,ethyleneglycolbutyl vinylether, hexanediol divinylether,triethyleneglycol methylvinylether, tetraethyieneglycol divinylether,trimethylolpropane trivinylether, aminopropyl vinylether,diethylaminoethyl vinylether, ethylene glycol divinyl ether,polyalkylene glycol divinyl ether, alkyl vinyl ether and3,4-dihydropyran-2-methyl 3,4-dihydropyran-2-carboxylate. Commercialvinyl ethers include the Pluriol-E200 divinyl ether (PEG200-DVE),poly-THF290 divinylether (PTHF290-DVE) and polyethyleneglycol-520 methylvinylether (MPEG500-VE) all of BASF Corp.

[0045] Hydroxy-functionalized mono(poly)vinylethers includepolyalkyleneglycol monovinylethers, polyalkylene alcohol-terminatedpolyvinylethers, butanediol monovinylether, cyclohexanedimethanolmonovinylether, ethyleneglycol monovinylether, hexanediolmonovinylether, diethyleneglycol monovinylether.

[0046] Another highly important class of vinyl ethers that are suitablefor stereolithography and may be used in the hybrid flexiblestereolithography compositions are all those included in the U.S. Pat.No. 5,506,087, which is incorporated herein by reference. More preferredare aromatic or alicyclic vinyl ethers. As an example, commercialvinylethers include Vectomer 4010, Vectomer 5015, Vectomer 4020,Vectomer 21010 and Vectomer 2020 of Allied Signal Corp., Morristown,N.J. Most preferred are Vectomer 4010 and Vectomer 5015.

[0047] Other cationically cured compounds include spiro ortho estersthat are prepared by reacting epoxy compounds with lactone;ethylenically unsaturated compounds, such as vinylcyclohexane,n-vinyl-2-pyrrolidone and its various derivatives, isobutylene andpolybutadiene, and derivatives of the above compounds.

[0048] The above cationically polymerizable compounds may be used aloneor as a mixture of two or more thereof depending upon the desiredperformance.

[0049] Additional cationically curable commercial products that can beused herein include:Uvacure 1500, Uvacure 1501, Uvacure 1502, Uvacure1530, Uvacure 1531, Uvacure 1532, Uvacure 1533, Uvacure 1534, Uvacure1561, Uvacure 1562, all commercial products of UCB Radcure Corp., Smyma,GA; UVR-6105, UVR-6100, UVR-6110, UVR-6128, UVR-6200, UVR-6216 of UnionCarbide Corp., Danburry, Conn.; the Araldite GY series that is BisphenolA epoxy liquid resins, the Araldite CT and GT series that is Bisphenol Aepoxy solid resins, the Araldite GY and PY series that is Bisphenol Fepoxy liquids, the cycloaliphatic epoxides Araldite CY 179 and PY 284,the Araldite DY and RD reactive diluents series, the Araldite ECN seriesof epoxy cresol novolacs, the Araldite EPN series of epoxy phenolnovolacs, all commercial products of Ciba Specialty Chemicals Corp., theHeloxy 48, Heloxy 44, Heloxy 84 and the other Heloxy product line, theEPON product line, all of Shell Corp., the DER series of flexiblealiphatic and Bisphenol A liquid or solid epoxy resins, the DEN seriesof epoxy novolac resins, all commercial products of Dow Corp., Celoxide2021, Celoxide 2021 P, Celoxide 2081, Celoxide 2083, Celoxide 2085,Celoxide 2000, Celoxide 3000, Glycidole, AOEX-24, Cyclomer A200,Cyclomer M-100, Epolead GT-300, Epolead GT-302, Epolead GT-400, Epolead401, Epolead 403, (Daicel Chemical Industries Co., Ltd.), Epicoat 828,Epicoat 812, Epicoat 872, Epicoat CT 508, (Yuka Shell Co., Ltd.),KRM-2100, KRM-2110, KRM-2199, KRM-2400, KRM-2410, KRM-2408, KRM-2490,KRM-2200, KRM-2720, KRM-2750 (Asahi Denka Kogyo Co., Ltd.).

[0050] It is possible to employ a host of known and industrially triedand tested cationic photoinitiators for epoxy resins for purposes ofpracticing the instant invention. Examples of these photoinitiators areonium salts with anions of weak nucleophilicity. Examples thereof arehalonium salts, iodosyl salts or sulfonium salts, sulfoxonium salts, ordiazonium salts, as described for example in U.S. Pat. No. 3,708,296.Other cationic photoinitiators are metallocene salts.

[0051] An overview of further commonplace onium salt initiators and/ormetallocene salts is offered by “UV-Curing, Science and Technology”,(Editor: S. P. Pappas, Technology Marketing Corp., 642 Westover Road,Stamford, Conn., USA) or “Chemistry & Technology of UV & EB Formulationsfor Coatings, Inks & Paints”, Vol. 3 (edited by P. K. T. Oldring), whichis incorporated herein by reference.

[0052] Preferred compositions comprise, as a cationic photoinitiator, acompound of the formula (B-I), (B-II) or (B-III)

[0053] in which R_(1B), R_(2B), R_(3B), R_(4B), R_(5B), R_(6B), andR_(7B) independently of one another are C₆-C₁₈ aryl which isunsubstituted or substituted by appropriate radicals, and

[0054] A⁻ is CF₃SO₃ ⁻ or an anion of the formula [LQ_(mB)]⁻, where

[0055] L is boron, phosphorus, arsenic or antimony,

[0056] Q is a halogen atom, or some of the radicals Q in an anion LQ_(m)⁻ may also be hydroxyl groups, and

[0057] mB is an integer corresponding to the valency of L enlarged by 1.

[0058] Examples of C₆-C₁₈ aryl in this context are phenyl, naphthyl,anthryl and phenanthryl. In these substituents present for appropriateradicals are alkyl, preferably C₁-C₆alkyl, such as methyl, ethyl,n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl, tert-butyl or thevarious pentyl or hexyl isomers, alkoxy, preferably C₁-C₆alkoxy, such asmethoxy, ethoxy, propoxy, butoxy, pentoxy or hexoxy, alkylthio,preferably C₁-C₆alkylthio, such as methylthio, ethylthio, propylthio,butylthio, pentylthio or hexylthio, halogen, such as fluorine, chlorine,bromine or iodine, amino groups, cyano groups, nitro groups or arylthio,such as phenylthio. Examples of preferred halogen atoms Q are chlorineand, in particular, fluorine. Preferred anions LQ_(mB) are BF₄ ⁻, PF₆ ⁻,AsF₆ ⁻, SbF₆ ⁻ and SbF₅(OH)⁻.

[0059] Particularly preferred compositions are those comprising as acationic photoinitiator a compound of the formula (B-III), in whichR_(5B), R_(6B)and R_(7B) are aryl, aryl being in particular phenyl orbiphenyl or mixtures of these two groups.

[0060] Further preferred compositions are those comprising as aphotoinitiator a compound of the formula (B-IV)

[0061] in which

[0062] cB is 1 or 2,

[0063] dB is 1, 2, 3, 4 or 5,

[0064] X_(B) is a non-nucleophilic anion, especially

[0065] PF₆ ⁻, AsF₆ ⁻, SbF₆ ⁻, CF₃SO₃ ⁻, C₂F₅SO₃ ⁻, n-C₃F₇SO₃ ⁻,n-C₄F₉SO₃ ⁻, n-C₆F₁₃SO₃ ⁻ and n-C₈F₁₇SO₃ ⁻,

[0066] R_(8B) is a π-arene and

[0067] R_(9B) is an anion of a π-arene, especially a cyclopentadienylanion.

[0068] Examples of π-arenes as R_(8B) and anions of π-arenes as R_(9B)can be found in EP-A-0 094 915. Examples of preferred π-arenes as R_(8B)are toluene, xylene, ethylbenzene, cumene, methoxybenzene,methylnaphthalene, pyrene, perylene, stilbene, diphenylene oxide anddiphenylene sulfide. Cumene, methylnaphthalene or stilbene areparticularly preferred. Examples of non-nucleophilic anions X⁻ are FSO₃⁻, anions of organic sulfonic acids, of carboxylic acids or of anionsLQ_(mB) ⁻. Preferred anions are derived from partially fluoro- orperfluoro-aliphatic or partially fluoro- or perfluoro-aromaticcarboxylic acids such as CF₃SO₃ ⁻, C₂F₅SO₃ ⁻, n-C₃F₇SO₃ ⁻, n-C₄F₉SO₃ ⁻,n-C₆F₁₃SO₃ ⁻, n-C₈F₁₇SO₃ ⁻, or in particular from partially fluoro- orperfluoro-aliphatic or partially fluoro- or perfluoro-aromatic organicsulfonic acids, for example from C₆F₅SO₃ ⁻, or preferably are anionsLQ_(mB) ⁻, such as BF₄ ⁻, PF₆ ⁻, AsF ₆ ⁻, SbF₆ ⁻, and SbF₅(OH)⁻.Preference is given to PF₆ ⁻, AsF₆ ⁻, SbF₆ ⁻, CF₃SO₃ ⁻, C₂F₅SO₃ ⁻,n-C₃F₇SO₃ ⁻, n-C₄F₉SO₃ ⁻, n-C₆F₁₃SO₃ ⁻ and n-C₈F₁₇SO₃ ⁻.

[0069] The metallocene salts can also be employed in combination withoxidizing agents. Such combinations are described in EP-A-0 126 712.

[0070] In order to increase the light yield it is possible, depending onthe type of initiator, also to employ sensitizers. Examples of these arepolycyclic aromatic hydrocarbons or aromatic keto compounds. Specificexamples of preferred sensitizers are mentioned in EP-A-0 153 904.

[0071] More preferred commercial cationic photoinitiators are UVI-6974,UVI-6970, UVI-6960, UVI-6990 (manufactured by Union Carbide Corp.),CD-1010, CD-1011, CD-1012 (manufactured by Sartomer Corp.), AdekaoptomerSP-150, SP-151, SP-170, SP-171 (manufactured by Asahi Denka Kogyo Co.,Ltd.), Irgacure 261 (Ciba Specialty Chemicals Corp.), CI-2481, CI-2624,CI-2639, CI-2064 (Nippon Soda Co, Ltd.), DTS-102, DTS-103, NAT-103,NDS-103, TPS-103, MDS-103, MPI-103, BBI-103 (MIdori Chemical Co, Ltd.).Most preferred are UVI-6974, CD-1010, UVI-6970, Adekaoptomer SP-170,SP-171, CD-1012, and MPI-103. The above-mentioned cationicphotoinitiators can be used either individually or in combination of twoor more.

[0072] It is possible to employ all types of photoinitiators which formfree radicals given the appropriate irradiation. Typical representativesof free-radical photoinitiators are benzoins, such as benzoin, benzoinethers, such as benzoin methyl ether, benzoin ethyl ether and benzoinisopropyl ether, benzoin phenyl ether and benzoin acetate,acetophenones, such as acetophenone, 2,2-dimethoxy-acetophenone and1,1-dichloroacetophenone, benzil, benzil ketals, such as benzildimethylketal and benzil diethyl ketal, anthraquinones, such as2-methylanthraquinone, 2-ethylanthra-quinone, 2-tert-butylanthraquinone,1-chloroanthraquinone and 2-amylanthraquinone, and alsotriphenylphosphine, benzoylphosphine oxides, for example2,4,6-trimethylbenzoyl-diphenylphosphine oxide (Luzirin® TPO),bisacylphosphine oxides, benzophenones, such as benzophenone and4,4′-bis(N,N′-dimethylamino)benzophenone, thioxanthones and xanthones,acridine derivatives, phenazine derivatives, quinoxaline derivatives or1-phenyl-1,2-propanedione 2-O-benzoyl oxime, 1-aminophenyl ketones or1-hydroxy phenyl ketones, such as 1-hydroxycyclohexyl phenyl ketone,phenyl 1-hydroxyisopropyl ketone and 4-isopropylphenyl1-hydroxyisopropyl ketone, all of which constitute known compounds.

[0073] Particularly suitable free-radical photoinitiators which are usedcustomarily in combination with a He/Cd laser as light source areacetophenones, such as 2,2-dialkoxybenzophenones and 1-hydroxy phenylketones, for example 1-hydroxycyclohexyl phenyl ketone or2-hydroxy-isopropyl phenyl ketone (=2-hydroxy-2,2-dimethylacetophenone),but especially 1-hydroxy-cyclohexyl phenyl ketone.

[0074] A class of photoinitiators that are commonly employed when usingargon ion lasers comprises the benzil ketals, for example benzildimethyl ketal. In particular, the photoinitiator used is an α-hydroxyphenyl ketone, benzil dimethyl ketal or2,4,6-trimethylbenzoyidiphenyl-phosphine oxide.

[0075] A further class of suitable photoinitiators constitutes the ionicdye-counterion compounds, which are capable of absorbing actinicradiation and of generating free radicals which are able to initiate thepolymerization of the acrylates. The novel compositions containing ionicdye-counterion compounds can in this way be cured more variably withvisible light in an adjustable wavelength range of 400-700 nm. Ionicdye-counterion compounds and their mode of action are known, for exampleU.S. Pat. Nos. 4,751,102, 4,772,530 and 4,772,541. Examples of suitableionic dye-counterion compounds are the anionic dye-iodonium ioncomplexes, the anionic dye-pyryllium ion complexes and, in particular,the cationic dye-borate anion compounds of the following formula:

[0076] in which D_(c) ⁺ is a cationic dye and R_(1C), R_(2C), R_(3C) andR_(4C) independently of one another are each an alkyl, aryl, alkaryl,allyl, aralkyl, alkenyl, alkynyl, an alicyclic or saturated orunsaturated heterocyclic group. Preferred definitions for the radicalsR_(1C) to R_(4C) can be taken for example, from EP-A-0 223 587.

[0077] As photoinitiator, the novel compositions preferably include a1-hydroxy phenyl ketone, especially 1-hydroxycyclohexyl phenyl ketone.

[0078] The free radical and cationic photoinitiators are added ineffective quantities, i.e. in quantities from 0.1 to 12, particularlyfrom 0.5 to 9 percent by weight, based on the overall quantity of thecomposition. If the novel compositions are used for stereolithographicprocesses, in which laser beams are normally employed, it is essentialfor the absorption capacity of the composition to be matched, by way ofthe type and concentration of the photoinitiators, in such a way thatthe depth of curing at normal laser rate is from approximately 0.1 to2.5 mm.

[0079] The novel mixtures may also contain various photoinitiators ofdifferent sensitivity to radiation of emission lines with differentwavelengths to obtain a better utilization of a UV/VIS light sourcewhich emits emission lines of different wavelengths. In this context itis advantageous for the various photoinitiators to be selected such, andemployed in a concentration such, that equal optical absorption isproduced with the emission lines used.

[0080] The free radically curable component preferably comprises atleast one solid or liquid poly(meth)acrylate, for example, be di-, tri-,tetra- or pentafunctional monomeric or oligomeric aliphatic,cycloaliphatic or aromatic acrylates or methacrylates. The compoundspreferably have a molecular weight of from 200 to 500.

[0081] Examples of suitable aliphatic poly(meth)acrylates having morethan two unsaturated bonds in their molecules are the triacrylates andtrimethacrylates of hexane-2,4,6-triol, glycerol or1,1,1-trimethylolpropane, ethoxylated or propoxylated glycerol or1,1,1-trimethylolpropane, and the hydroxyl-containing tri(meth)acrylateswhich are obtained by reacting triepoxide compounds, for example thetriglycidyl ethers of said triols, with (meth)acrylic acid. It is alsopossible to use, for example, pentaerythritol tetraacrylate,bistrimethylolpropane tetraacrylate, pentaerythritolmonohydroxytriacrylate or -methacrylate, or dipentaerythritolmonohydroxypentaacrylate or -methacrylate.

[0082] It is additionally possible, for example, to use polyfunctionalurethane acrylates or urethane methacrylates. These urethane(meth)acrylates are known to the person skilled in the art and can beprepared in a known manner by, for example, reacting ahydroxyl-terminated polyurethane with acrylic acid or methacrylic acid,or by reacting an isocyanate-terminated prepolymer with hydroxyalkyl(meth)acrylates to give the urethane (meth)acrylate.

[0083] Examples of suitable aromatic tri(meth)acrylates are the reactionproducts of triglycidyl ethers of trihydric phenols and phenol or cresolnovolaks containing three hydroxyl groups, with (meth)acrylic acid.

[0084] The (meth)acrylates used herein are known compounds and some arecommercially available, for example from the SARTOMER Company underproduct designations such as SR®295, SR®350, SR®351, SR®367, SR®399,SR®444, SR®454 or SR®9041.

[0085] Preferred compositions are those in which the free radicallycurable component contains a tri(meth)acrylate or a penta(meth)acrylate.

[0086] Suitable examples of di(meth)acrylates are the di(meth)acrylatesof cycloaliphatic or aromatic diols such as1,4-dihydroxymethylcyclohexane, 2,2-bis(4-hydroxy-cyclohexyl)propane,bis (4-hydroxycyclohexyl)methane, hydroquinone, 4,4′-dihydroxybi-phenyl,Bisphenol A, Bisphenol F, bisphenol S, ethoxylated or propoxylatedBisphenol A, ethoxylated or propoxylated Bisphenol F or ethoxylated orpropoxylated bisphenol S. Di(meth)acrylates of this kind are known andsome are commercially available.

[0087] Other di(meth)acrylates which can be employed are compounds ofthe formulae (F-I), (F-II), (F-III) or (F-IV)

[0088] in which

[0089] R_(1F) is a hydrogen atom or methyl,

[0090] Y_(F) is a direct bond, C₁-C₆alkylene, —S—, —O—, —SO—, —SO₂— or—CO—,

[0091] R_(2F) is a C₁-C₈alkyl group, a phenyl group which isunsubstituted or substituted by one or more C₁-C₄alkyl groups, hydroxylgroups or halogen atoms, or is a radical of the formula —CH₂—OR_(3F) inwhich

[0092] R_(3F) is a C₁-C₈alkyl group or phenyl group, and

[0093] A_(F) is a radical selected from the radicals of the formulae

[0094] Further examples of possible di(meth)acrylates are compounds ofthe formulae (F-V), (F-VI), (F-VII) and (F-VIII)

[0095] These compounds of the formulae (F-I) to (F-VIII) are known andsome are commercially available. Their preparation is also described inEP-A-0 646 580.

[0096] Examples of commercially available products of thesepolyfunctional monomers are KAYARAD R-526, HDDA, NPGDA, TPGDA; MANDA,R-551, R-712, R-604, R-684, PET-30, GPO-303, TMPTA, THE-330, DPHA-2H,DPHA-2C, DPHA-21, D-310, D-330, DPCA-20, DPCA-30, DPCA-60, DPCA-120,DN-0075, DN-2475, T-1420, T-2020, T-2040, TPA-320, TPA-330, RP-1040,R-011, R-300, R-205 (Nippon Kayaku Co., Ltd.), Aronix M-210, M-220,M-233, M-240, M-215, M-305, M-309, M-310, M-315, M-325, M-400, M-6200,M-6400 (Toagosei Chemical Industry Co, Ltd.), Light acrylate BP-4EA,BP-4PA, BP-2EA, BP-2PA, DCP-A (Kyoeisha Chemical Industry Co., Ltd.),New Frontier BPE-4, TEICA, BR-42M, GX-8345 (Daichi Kogyo Seiyaku Co.,Ltd.), ASF-400 (Nippon Steel Chemical Co.), Ripoxy SP-1506, SP-1507,SP-1509, VR-77, SP-4010, SP-4060 (Showa Highpolymer Co., Ltd.), NK EsterA-BPE-4 (Shin-Nakamura Chemical Industry Co., Ltd.), SA-1002 (MitsubishiChemical Co., Ltd.), Viscoat-195, Viscoat-230, Viscoat-260, Viscoat-310,Viscoat-214HP, Viscoat-295, Viscoat-300, Viscoat-360, Viscoat-GPT,Viscoat-400, Viscoat-700, Viscoat-540, Viscoat-3000, Viscoat-3700 (OsakaOrganic Chemical lndustry Co., Ltd.).

[0097] According to the present invention, it is preferrable that theradiation-curable and cationically polymerizable organic component (a)comprise at least one component (a1) that is a polyfunctional aliphatic,alicyclic or aromatic glycidylether(s) having at least three epoxygroups per molecule. Component (a1) has been found to 1) substantiallyincrease the high temperature performance of the cured article, 2)improve the wet recoatability of the liquid composition and 3) improvethe side wall finish of the cured article. More preferred compositionscontain component (a1) that is a polyfunctional aliphatic, alicyclic oraromatic glycidylether, or mixtures thereof having at least three epoxygroups per molecule with an epoxy equivalent weight (EEW) between 90 and800. Most preferred are those having an EEW weight between 90 and 650.The triglycidylether of trimethylolpropane, Heloxy 48 of Shell Corp.,having an EEW of about 140-160 is one of the most preferredpolyglycidylether compounds. The polyfunctional glycidylether(s) havingat least three epoxy groups in their molecule preferably comprisesbetween about 2 and 90% by weight the overall cationic component (a),more preferably, between about 9 and about 60% by weight, mostpreferably betweeh 10 and 50% by weight.

[0098] According to the present invention, it is preferrable that theradiation-curable and cationically polymerizable organic component (a)comprise at least one component (a2) that is an alicyclic polyepoxidehaving at least two epoxy groups per molecule. Component (a2) has beenfound to be effective at increasing the high temperature performance ofcured articles when it is in a very pure form, which means eliminationof its dimers or trimers at the highest possible extent. More preferredcompositions contain component (a2) with a monomer purity of over about80% and epoxy equivalent weight between 80 and 330, more preferablybetween 90 and 300. Most preferred compositions contain component (a2)in a pure form having epoxy equivalent weight between 100 and 280wherein dimers or trimers or oligomers are substantially eliminated.Commercial products having over about 90% monomer purity to greater thanabout 94% monomer purity are most preferred. For example,3,4-epoxycyclohexylmethyl 3′, 4′-epoxycyclohexanecarboxylate (ECEC)having an epoxy equivalent weight between 130 and 145 with varyingdegrees of monomer purity can be purchased through various commercialsources. More preferred is Araldite CY179 of Ciba Speciality Chemicalscontaining a limited percentage of dimers or oligomers, such that themonomer purity is about 90%. Most preferred is UVR6105 of Union CarbideCorp., which contains a smaller percentage of oligomers than Araldite CY179. The most preferred is Uvacure 1500 of UCB Radcure Corp., which isthe purest ECEC known by the inventors. Table 1 in the exampledemonstrate that the high monomer purity of Uvacure 1500 produces acured article having an unusually high thermal performance. Even a smallpercentage by weight of dimers or trimers in a cycloaliphatic epoxide,component (a2), can drastically reduce the HDT value of the curedarticle. Preferred compositions contain component (a2) at between 5 to80% by weight. More preferred compositions contain component (a2) atbetween 10 and 75% by weight. Most preferred compositions containcomponent (a2) at between 15 to 70% by weight.

[0099] According to the present invention, it is preferrable that theradiation-curable and cationically polymerizable organic component (a)comprise at least one component (a3) that is a solid or liquidepoxycresol novolac or epoxyphenol novolac having at least two epoxygroups per molecule. Component (a3) has been found to be very effectiveat increasing the high temperature performance of cured articles whenits epoxy functionality becomes higher than 2. The epoxy equivalentweight of component (a3) is between 130 to 350 g/eq. More preferredcompositions contain component (a3) that is epoxycresol novolac orepoxyphenol novolacs having an epoxy functionality at least about 3.Most preferred are those with epoxy functionality over about 4 togreater than about 5. For example, epoxycresol novolac ECN1299 has anepoxy equivalent weight number between 217 and 244 with an epoxyfunctionality of about 5.4 (product of Ciba Specilaty Chemicals) andproduces a cured article having high temperature performance. Preferredamounts for component (a3) is between 3 and 80% by weight. Morepreferred amount is between 8 to 75% by weight. The most preferredamount is between 10 to 55% by weight.

[0100] Component (a) optionally preferably includes vinyl-ether groupcontaining compounds. Preferred examples are aliphatic polyalkoxydi(poly)vinylethers, polyalkylene di(poly)vinylethers andhydroxy-functionalized mono(poly)vinylethers. More preferred vinylethersare those having aromatic or alicyclic moities in their molecules.Preferred amounts of the vinylether component is between 0.5 to 20% byweight. More preferred amounts is between 2 to 17% by weight. Mostpreferred amounts is between 3 to 14 by weight.

[0101] According to the present invention, it is preferrable thatradiation curable and radically polymerizable organic component (c) becontained in amounts of 4 to 35% by weight. More referred compositionscontain component (c) between 7 to 30% by weight. Most preferred arecompositions containing component (c) between 8 to 20% by weight. Mostpreferred compositions also contain 4 to 10% by weight of at least oneliquid or solid poly(meth)acrylate having a (meth)acrylate functionalitygreater than or equal to 3, and from 4 to 10% by weight of one or moredi(meth)acrylates.

[0102] Preferred compositions contain component (b) that is a cationicphotoinitiator or a mixture of cationic photoinitiators between 0.05 to12% by weight. More preferred compositions contain component (b) between0.1 to 11% by weight. Most preferred compositions contain component (b)between 0.15 to 10% by weight.

[0103] It is preferred for component (d) that is a free-radicalphotoinitiator or a mixture of free-radical photoinitiators to becontained between 0.1 to 10% by weight. More preferred compositionscontain component (d) between 0.3 to 8% by weight. Most preferredcompositions contain component (d) between 0.4 to 7% by weight.

[0104] Preferred, more preferred and most preferred compositions maycontain between 0 to 10% by weight of additives or reactive diluents.

[0105] To impart flexibility and impact resistance, the novelcompositions herein optionally further include a cationic reactivemodifier (epoxy-, vinylether-, spiro-orthoester- or oxetane-based). Thecationic reactive modifier component imparts flexibility and impactresistance to the cured article without compromising photospeed, oraccuracy of the liquid composition or water resistance for the curedarticle. The selected cationic reactive modifiers should be at leastbifunctional compounds, more preferably aliphatic, alicyclic and/oraromatic compounds having, on average, at least two cationicallyreactive groups per molecule containing at least one chain extensionsegment with a molecular weight of at least about 100 and not more than2000. Each chain extension segment is an organic or inorganic chain thatconnects the epoxide rings or vinylether groups or other cationicallyreactive groups with the core or backbone of the main molecule. Theequivalent weight per epoxide can vary between about 180 and about 2000.The equivalent weight per vinylether group or any other cationicallycured group can vary between about 100 and 1600.

[0106] Cationic reactive modifiers having more than two cationicallyreactive groups and a corresponding number of chain extension segmentsare preferred. Preferred chain extension segments are unsubstitutedaliphatic or aliphatic substituted with C₁-C₁₀alkyl or C₁-C₁₀alkoxygroups, unsubstituted alkylene or substituted with C₁-C₁₀alkyl orC₁-C₁₀alkoxy alkylene groups, unsubstituted cycloaliphatic orsubstituted cycloaliphatic with C₁-C₁₀ alkyl or C₁-C₁₀alkoxy groups,unsubstituted aromatic or aromatic substituted with C₁-C₁₀alkyl orC₁-C₁₀alkoxy groups, saturated and unsaturated polyesters, polyethers,polysiloxanes, polysilanes, polycarbonates, polyalkylene ethers. A chainextension segment having 4 to 60 repeating C₂-C₄alkoxy groups, forexample isopropoxy, propoxy and ethoxy, is most preferred. Similarly,for aromatic epoxides, the chain extension segment between the glycidylether groups and the aromatic nucleus of polyhydric alcohol should havea molecular weight of at least about 100 and not more than 2000.

[0107] Also preferred are polyglycidyl esters andpoly(β-methylglycidyl)esters having chain extension segments having amolecular weight of at least about 100 and not more than 2000. Saidcompounds can be obtained by reacting a compound having at least twocarboxyl groups in the molecule with epichlorohydrin or glyceroldichlorohydrin or β-methylepichlorohydrin. Likewise, it is possible toemploy cycloaliphatic polycarboxylic acids, for exampletetrahydrophthalic acid. It is also possible to use aromaticpolycarboxylic acids such as phthalic acid,pyromellitic acid, or elsecarboxyl-terminated adducts, for example of trimellitic acid andpolyols, for example glycerol or 2,2-bis(4-hydroxycyclohexyl)propane.

[0108] Epoxidized oils (e.g. the Union Carbide FLEXOL, LOE or EPO)having chain extension segments having a molecular weight of at leastabout 400 and not more than 3,000 are also preferred epoxy-basedcationic reactive modifiers.

[0109] A more preferred epoxy-based cationic reactive modifier is aliquid or solid polyglycidyl ether of a polyhydric alcohol or adducts orpolybasic acid thereof with alkylene oxide (e.g. triglycidyl ether ofglycerol chain extended by between five and fourteen isopropoxy groupsper glycidyl ether group). Also preferred is a dimer aciddiglycidylether having an aliphatic backbone of between about C₁₅ toabout C₁₅₀, such as Heloxy® 71 having an aliphatic backbone of aboutC₃₄, polyglycol diepoxides having a backbone consisting between about 4and 50 isopropoxy units, such as Heloxy® 32, with 7 isopropoxy groups,polyglycidylethers of castor oil, such as Heloxy® 505, all threeproducts are commercially available by Shell Corp., Houston, Tex. Themost preferred epoxy-based cationic reactive modifier is a triglycidylether of polypropoxylated glycerol having the following structure:

[0110] which is commercially available under the tradename Heloxy® 84from Shell Company, Houston, Tex.

[0111] Other preferred cationic reactive modifiers are based on liquidor solid vinyl ethers, such as polyalkylene glycol di-(poly) vinylether, tetraethyleneglycol divinylether, hydroxy-functionalizedmono(poly)vinylethers, also cycloaliphatic or aromatic (di)polyvinylethers chain extended with at least one chain extension segment.Preferred chain extension segments are unsubstituted aliphatic oraliphatic substituted with C₁-C₁₀alkyl or C₁-C₁₀alkoxy groups,unsubstituted alkylene or alklylene substituted with C₁-C₁₀alkyl orC₁₀-C₁₀alkoxy groups, unsubstituted cycloaliphatic or cycloaliphaticsubstituted with C₁-C₁₀alkyl or C₁-C₁₀alkoxy groups, unsubstitutedaromatic or aromatic substituted with C₁-C₁₀alkyl or C₁-C₁₀alkoxygroups, saturated and unsaturated polyesters, polyethers, polysiloxanes,polysilanes, polycarbonates, polyalkylene ethers. The vinylether-basedcationic reactive modifier should be at least bifunctional.

[0112] A chain extension segment having 4 to 80 repeating C₂-C₄alkoxygroups, for example isopropoxy, propoxy and ethoxy, is most preferred.

[0113] Depending on the polarity of the composition, the chain extensionsegment can be chosen in such a way that the cationic reactive modifieris highly compatible with the liquid curable composition. Such aselection results in, not only an improvement in elongation and impactresistance, but improved recoatability and elimination of undesirablephase separation phenomena. In the case of slightly polar liquidcompositions, the chain extension segment may be an ethoxy or propoxy orisopropoxy or oxytetramethylene or derivatives thereof. In addition tohigh flexibility, if there is a need for imparting water resistance intothe composition, then the aromatic or hydrocarbon or isopropoxy or lowether content chain extenders are most preferred.

[0114] The cationic reactive modifiers are preferably present in theoverall composition at between about 0.5% to about 60% by weight, morepreferably about 2% to about 50% by weight, most preferably about 2% to30 by weight. The solid or liquid reactive cationically modifiers may beused singly or as a mixture.

[0115] The compositions described above can further include customaryadditives for stereolithographic compositions, such as coloring agents,such as pigments and dyes, antifoaming agents, leveling agents,thickening agents, flame retardant and antioxidants.

[0116] In a particularly preferred embodiment, the hybrid cationicallyand radically cured composition does not contain any polyol or hydroxylgroup-containing compounds. It has been widely accepted that hydroxylgroup-containing compounds are a required component for epoxy hybridcompositions used in stereolithography. It is believed that epoxyformulations do not cure and postcure to high extent unless thecomposition contains a certain percentage of a diol, triol or polyol.This belief is based on the understanding that the hydroxyl groups reactwith the epoxy groups during the epoxy ring opening, and contribute tothe formation of a dense three dimensional network. A recent applicationWO 97/38354 (Oct. 16, 1997) to DSM Corp., Japan Synthetic Rubber Co.,Ltd., Japan Fine Coatings Co., Ltd. teaches that a diol or trio orpolyol component is necessary to be present in a hybrid liquidcomposition at a concentration above a critical one in order the curedarticles to possess good properties. The same patent teaches that “ifthe proportion of the polyol component is too low, the aim of developingthe photo-curing characteristic can not be achieved and these are caseswhere a three-dimensional object with sufficient stability in shape andproperties can not be produced from the resin composition”. Applicants,however, herein have been able to obtain highly crosslinked networks byphotopolymerizing hybrid epoxy compositions with no diol or triol orpolyol having high heat deflection temperature values, in excess 110° C.

[0117] If necessary, the resin composition for stereolithographyapplications according to the present invention may contain othermaterials in suitable amounts, as far as the effect of the presentinvention is not adversely affected. Examples of such materials includeradical-polymerizable organic substances other than the aforementionedcationically polymerizable organic substances; heat-sensitivepolymerization initiators; various additives for resins such as coloringagents such as pigments and dyes, antifoaming agents, leveling agents,thickening agents, flame retardant and antioxidant; fillers such assilica, alumina, glass powder, ceramic powder, metal powder and modifierresins. Particular examples of the radical-polymerizable organicsubstances include but not limited to compounds that thermallypolymerize, while those of the heat-sensitive polymerization initiatorincludes aliphatic onium salts disclosed in Japanese Patent Laid-OpenNos. 49613/1982 and 37004/1983.

[0118] The filler to be used in the present invention is a reactive ornon-reactive, inorganic or organic, powdery, fibrous or flaky material.The filler material can be organic or inorganic. Examples of organicfiller materials are polymeric compounds, thermoplastics, core-shell,aramid, kevlar, nylon, crosslinked polystyrene, crosslinked poly(methylmethacrylate)., polystyrene or polypropylene, crosslinked polyethylenepowder, crosslinked phenolic resin powder, crosslinked urea resinpowder, crosslinked melamine resin powder, crosslinked polyester resinpowder and crosslinked epoxy resin powder. Examples of inorganic fillersare mica, glass or silica beads, calcium carbonate, barium sulfate,talc, glass or silica bubbles, zirconium silicate, iron oxides, glassfiber, asbestos, diatomaceous earth, dolomite, powdered metals, titaniumoxides, pulp powder, kaoline, modified kaolin, hydrated kaolin metallicfilers, ceramics and composites. Mixtures of organic and/or inorganicfillers can be used.

[0119] Further examples of preferred fillers are micro crystallinesilica, crystalline silica, amorphous silica, alkali alumino silicate,feldspar, woolastonite, alumina, aluminum hydroxide, glass powder,alumina trihydrate, surface treated alumina trihydrate, aluminasilicate. Each of the preferred fillers is commercially available. Themost preferred filler materials are inorganic fillers, such as mica,Imsil, Novasite, amorphous silica, feldspar, and alumina trihydrate. Ithas transparency to UV light, low tendency to refract or reflectincident light and it provides good dimensional stability and heatresistance.

[0120] The filler to be used for the resin composition forstereolithography according to the present invention must satisfyrequirements that it hinders neither cationic nor radicalpolymerizations and the filled SL composition has a relatively lowviscosity suitable for the stereolithography process. These fillers maybe used alone or as a mixture of two or more of them depending upon thedesired performance. The fillers used in the present invention may beneutral acidic or basic. The filler particle size may vary depending onthe application and the desired resin characteristics. It may varybetween 50 nanometers and 50 micrometers.

[0121] The filler material can optionally be surfaced treated withvarious compounds-coupling agents. Examples include methacryloxy propyltrimethoxy silane, beta-(3,4-epoxycyclohexyl)ethyl trimethoxy silane,gamma-glycidoxy propyl trimethoxy silane and methyl triethoxy silane.The most preferred coupling agents are commercially available from OsiChemicals Corp. and other chemical suppliers.

[0122] The filler loading is preferably from about 0.5 to about 90%,more preferably from about 5 to about 75%, most preferably from about 5to about 60% by weight with respect to the total weight of the filledresin composition.

[0123] The novel compositions can be prepared in a known manner by, forexample, premixing individual components and then mixing these premixes,or by mixing all of the components using customary devices, such asstirred vessels, in the absence of light and, if desired, at slightlyelevated temperature.

[0124] The novel compositions can be polymerized by irradiation withactinic light, for example by means of electron beams, X-rays, UV or VISlight, preferably with radiation in the wavelength range of 280-650 nm.Particularly suitable are laser beams of HeCd, argon or nitrogen andalso metal vapour and NdYAG lasers. This invention is extendedthroughout the various types of lasers existing or under developmentthat are to be used for the stereolithography process, e.g. solid state,argon ion lasers,etc. The person skilled in the art is aware that it isnecessary, for each chosen light source, to select the appropriatephotoinitiator and, if appropriate, to carry out sensitization. It hasbeen recognized that the depth of penetration of the radiation into thecomposition to be polymerized, and also the operating rate, are directlyproportional to the absorption coefficient and to the concentration ofthe photoinitiator. In stereolithography it is preferred to employ thosephotoinitiators which give rise to the highest number of forming freeradicals or cationic particles and which enable the greatest depth ofpenetration of the radiation into the compositions which are to bepolymerized.

[0125] The invention additionally relates to a method of producing acured product, in which compositions as described above are treated withactinic radiation. For example, it is possible in this context to usethe novel compositions as adhesives, as coating compositions, asphotoresists, for example as solder resists, or for rapid prototyping,but especially for stereolithography. When the novel mixtures areemployed as coating compositions, the resulting coatings on wood, paper,metal, ceramic or other surfaces are clear and hard. The coatingthickness may vary greatly and can for instance be from 0.01 mm to about1 mm. Using the novel mixtures it is possible to produce relief imagesfor printed circuits or printing plates directly by irradiation of themixtures, for example by means of a computer-controlled laser beam ofappropriate wavelength or employing a photomask and an appropriate lightsource.

[0126] One specific embodiment of the abovementioned method is a processfor the stereolithographic production of a three-dimensional shapedarticle, in which the article is built up from a novel composition withthe aid of a repeating, alternating sequence of steps (a) and (b); instep (a), a layer of the composition, one boundary of which is thesurface of the composition, is cured with the aid of appropriateradiation within a surface region which corresponds to the desiredcross-sectional area of the three-dimensional article to be formed, atthe height of this layer, and in step (b) the freshly cured layer iscovered with a new layer of the liquid, radiation-curable composition,this sequence of steps (a) and (b) being repeated until an articlehaving the desired shape is formed. In this process, the radiationsource used is preferably a laser beam, which with particular preferenceis computer-controlled.

[0127] In general, the above-described initial radiation curing, in thecourse of which the so-called green models are obtained which do not asyet exhibit adequate strength, is followed then by the final curing ofthe shaped articles by heating and/or further irradiation.

[0128] The term “liquid” in this application is to be equated with“liquid at room temperature” in the absence of any statement to thecontrary, room temperature being understood as being, in general, atemperature between 50 and 45° C., preferably between 15° and 30° C.

EXAMPLES BACKGROUND

[0129] Representative embodiments of the present invention will bedescribed as examples, though the present invention by no means islimited by them. In the following examples, all parts are by weight. Theformulations indicated in the examples are prepared by mixing thecomponents, with a stirrer at 20 to 80° C. (depending on viscosity)until a homogeneous composition is obtained. Most formulations can bestirred to a homogenous composition at room temperatures of about 25 to30° C.

[0130] The physical data relating to the formulations are obtained asfollows: The viscosity of the liquid mixture is determined at 30° C.using a Brookfield viscometer. The mechanical properties of theformulations are determined on three-dimensional specimens produced withthe aid of an He/Cd or Ar/UV laser. In particular, the window panes (formeasuring photospeed) and the HDT specimens were built in a 3D SystemsSL 350 sterelithography machine using a solid state laser emitting at355 nm. The HDT specimens were UV postcured in a 3D PCA apparatus for 90minutes and subsequently thermally postcured at 160° C. for 2 hours. TheHDT value was measured based on the ASTM method D648 under maximum fiberstress of 66 psi.

[0131] The photosensitivity of the formulations is determined onso-called window panes. In this determination, single-layer testspecimens are produced using different laser energies, and the layerthicknesses obtained are measured. The plotting of the resulting layerthickness on a graph against the logarithm of the irradiation energyused gives a“working curve”. The slope of this curve is termed D_(p)(given in mm or mils). The energy value at which the curve passesthrough the x-axis is termed E_(c) (and is the energy at which gellingof the material still just takes place; cf. P. Jacobs, Rapid Prototypingand Manufacturing, Soc. of Manufacturing Engineers, 1992, p. 270 ff.).

[0132] The raw materials used for liquid SL compositions of Table 1were:

[0133] Trimethylolpropane triglycidylether (Heloxy 48) and4,4′-cyclohehanedimethanol diglycidylether (Heloxy 107) are commercialproducts of Shell Corp., Houston, Tex.

[0134] 1,4-Butanediol diglycidylether (Araldite DY026), cresol epoxynovolac (ECN1299), epoxy phenol novolac (EPN 9880CH),3,4-epoxycyclohexylmethyl 3′,4′-epoxycyclohexanecarboxylate (AralditeCY179), and radical photoinitiator 1-hydroxycyclohexyl phenyl ketone(Irgacure 184), are all commercial products of Ciba Specialty ChemicalsCorp., Tarrytown, N.Y.

[0135] 3,4-epoxycyclohexylmethyl 3′,4′-epoxycyclohexanecarboxylate(UVAcure1500), is a distilled cycloaliphatic diepoxide, and theBisphenol A diglycidylether diacrylate (Ebecryl 3700) are commercialproducts of UCB Radcure, Smyrna, Ga.

[0136] Dipentaerythritol monohydroxypentaacrylate (SR 399) and thecationic photoinitiator CD1010 are commercial products of Sartomer Corp,Exton, Pa.

[0137] Caprolactone polyester-polyol Tone 0301 is a commercial productof Union Carbide, Danbury, Conn. TABLE 1 Liquid StereolithographyCompositions. Formula # 1 2 3 4 5 6 7 8 Heloxy 48 15.0 30.0 30.0 10.010.0 30.0 Heloxy 107 30.0 12.5 12.5 DY 026 30.0 20.0 20.0 ECN 1299 38.2EPN 9880 38.2 CH UVACure 65.2 50.2 50.2 50.2 50.2 1500 CY 179 50.2Vectomer 8.0 4010 N3700 6.3 6.3 6.3 6.3 6.3 6.3 6.3 6.3 SR399 6.0 6.06.0 6.0 6.0 6.0 6.0 6.0 I-184 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 CD 10105.0 5.0 5.0 5.0 5.0 4.5 4.5 5.0 Total 100.0 100.0 100.0 100.0 100.0100.0 100.0 108.0 Weight D_(p) (mils) 5.46 5.48 5.57 5.26 5.59 4.86 4.845.39 E_(c) 8.85 8.54 7.39 6.75 10.05 14.38 21.35 6.06 (mJ/cm²) HDT, 2 hat 215 254 129 130 141 240 110 208 160° C.

[0138] Compositions 1 and 2 produce cured articles having excellent heatdeflection temperature values due to the presence of Uvacure 1500, apurified cycloaliphatic epoxide with epoxy equivalent weight between 130and 145, in conjuction with Heloxy 48, a polyglycidylether componenthaving at least three epoxy groups and epoxy equivalent weight between140 and 160. Composition 3 shows a drop of about 125° C. of the HDTvalue compared to that of composition 2. This trend was attributed tothe replacement of Heloxy 48 of composition 2 with Heloxy 107, adifunctional glycidylether in composition 3; note that Heloxy 48 andHeloxy 107 have very similar epoxy equivalent weight, and are containedat the same percentage by weight. A similar trend was observed incomposition 4 where introduction of the Araldite DY 026, a difunctionalaliphatic epoxide with epoxy equivalent weight of between 120-135instead of Heloxy 48 (as in composition 2) may be responsible forlowering the HDT value to about 130° C. Composition 5 is similar tocomposition 2 except that Uvacure 1500 has been replaced with AralditeCY 179. Araldite CY179 is an alicyclic epoxide having substantially thesame chemical structure as UVAcure 1500. Without being bound by anytheories, the lower HDT value of composition 5 relative to composition 2may be attributed to the fact that CY179 has a lower monomer purity thanUVAcure1500. Composition 6 produces excellent heat deflectiontemperature value due to the incorporation of ECN 1299 (epoxy cresolnovolac), which has a very high number of reactive functionality(approximately 5.4). Composition 7 containing an epoxy phenol novolacshows HDT value that is higher than the commercially available hybridstereolithography resins having HDT values between 80 and 100° C.Replacement of the EPN9880CH component (epoxy functionality of 3.6) withanother epoxy phenol novolac having epoxy functionality over 4 wouldyield a cured article with much higher HDT value than composition 7.Composition 8 shows that incorporation of a vinylether, Vectomer 4010,improves the photospeed of the liquid composition while maintaining highthermal resistance.

[0139] The above-mentioned scientific comments on SL liquid compositionsof Table 1 were provided in an attempt to follow the trend of thermalproperties based on individual components. Our intention was neither todistinguish amongst good or bad SL liquid compositions nor to be boundby any theories. In addition to high HDT values, the compositions shownabove exhibit high photospeed, good wet-recoatability properties, highwater resistance and good side wall finish.

What is claimed is:
 1. A novel resin composition comprising a) 55-90% byweight of at least one solid or liquid actinic radiation-curable andcationically polymerizable organic substance; b) 0.05 to 10% by weightan actinic radiation-sensitive initiator for cationic polymerization; c)5% to 25% by weight of an actinic radiation-curable andradical-polymerizable organic substance; and (d) 0.02 to 10% by weightan actinic radiation-sensitive initiator for radical polymerization,wherein component (a) comprises at least one glycidylether of apolyhydric aliphatic, alicyclic or aromatic alcohol having at leastthree epoxy groups with epoxy equivalent weight between 90 and 800g/equivalent and at least one solid or liquid alicyclic epoxide withepoxy equivalent weight between 80 and 330 having at least two epoxygroups with a monomer purity of at least about 80% by weight, ormixtures thereof with the sum total of components (a) through (d) being100 percent by weight.
 2. A liquid composition according to claim 1wherein component (a) comprises the at least one solid or liquidalicyclic epoxide having at least two epoxy groups, or mixtures thereof,at between 20 and 75% by weight.
 3. A liquid composition according toclaim 1 wherein component (a) further comprises not more than 20% byweight of at least one liquid or solid vinylether compound having atleast two cationically-reactive groups in the molecule or ahydroxy-functionalized mono(poly)vinylether or mixtures thereof.
 4. Aliquid composition according to claim 1 wherein component (a) furthercomprises at least one liquid or solid epoxy cresol novolac, epoxyphenol novolac, oxetane or spiro-ortho ester compound having at leasttwo cationically-reactive groups in the molecule, or mixtures thereof.5. A liquid composition according to claim 1 wherein the at least oneglycidylether of a polyhydric aliphatic, alicyclic or aromatic alcoholhaving at least three epoxy groups is between 3 and 90% by weight of theat least one alicylic epoxide having at least two epoxy groups.
 6. Aliquid composition according to claim 5 wherein the at least oneglycidylether of a polyhydric alcohol having at least three epoxy groupscomprises at least 15% by weight of the at least one alicylic epoxidehaving at least two epoxy groups.
 7. A novel resin compositioncomprising a) 55-90% by weight of at least one solid or liquid actinicradiation-curable and cationically polymerizable organic substance; b)0.05 to 10% by weight an actinic radiation-sensitive initiator forcationic polymerization; c) 5-25% by weight of an actinicradiation-curable and radical-polymerizable organic substance; and (d)0.02 to 10% by weight an actinic radiation-sensitive initiator forradical polymerization, wherein component (a), comprises of at least oneglycidylether of a polyhydric aliphatic, alicyclic or aromatic alcoholhaving at least three epoxy groups with epoxy equivalent weight between90 and 800 g/equivalent and at least one solid or liquid epoxy cresolnovolac, or epoxy phenol novolac with epoxy equivalent weight between130 and 350 having at least two functional groups, or mixtures thereofwith the sum total of components (a) through (d) being 100 percent byweight.
 8. A liquid composition according to claim 7 wherein component(a) comprises the at least one solid or liquid epoxy cresol novolac,epoxy phenol novolac having at least two functional groups, or mixturesthereof between 2 and 50% by weight.
 9. A novel composition according toclaim 7 wherein component (a) further comprises not more than 20% byweight of at least one liquid or solid vinylether compound having atleast two cationically-reactive groups in the molecule, or ahydroxy-functionalized mono(poly)vinylether, or mixtures thereof.
 10. Anovel composition according to claim 7 wherein component (a) furthercomprises at least one liquid or solid alicyclic polyfunctional epoxide,oxetane or spiro-ortho ester compound having at least twocationically-reactive groups in the molecule, or mixtures thereof.
 11. Aliquid composition according to claim 7 wherein the at least oneglycidylether of a polyhydric aliphatic, alicyclic or aromatic alcoholhaving at least three epoxy groups is between 3 and 90% by weight of theat least one solid or liquid epoxy cresol novolac, epoxy phenol novolachaving at least two functional groups.
 12. A curable compositionaccording to claim 7 wherein the at least one glycidylether of apolyhydric aliphatic, alicyclic or aromatic alcohol having at leastthree epoxy groups is at least 15% by weight of the at least one solidor liquid epoxy cresol novolac, epoxy phenol novolac having at least twofunctional groups.
 13. A curable composition according to claim 7wherein the at least one solid or liquid epoxy cresol novolac or epoxyphenol novolac having at least two functional groups has an epoxyfunctionality at least 4.5.
 14. A curable composition according to claim1 wherein the composition further comprises: e) 0.5 to about 40 percentby weight of at least one solid or liquid cationic reactivemodifier-flexibilizer.
 15. A curable composition according to claim 14wherein the at least one solid or liquid cationic reactive modifier is areactive epoxy modifier or reactive vinylether modifier or mixturesthereof.
 16. A curable composition according to claim 14 wherein thereactive modifier-flexibilizer comprises at least one cationicallyreactive bifunctional aliphatic, alicyclic or aromatic compoundcontaining a chain extension segment connected to the cationic reactivegroup with a molecular weight of at least about 100 and not more than2000.
 17. A curable composition according to claim 7 wherein thecomposition further comprises: e) 0.5 to about 40 percent by weight ofat least one solid or liquid cationic reactive modifier-flexibilizer.18. A curable composition according to claim 17 wherein the at least onesolid or liquid cationic reactive modifier is a reactive epoxy modifieror reactive vinylether modifier or mixtures thereof.
 19. A curablecomposition according to claim 17 wherein the reactivemodifier-flexibilizer comprises at least one cationically reactivebifunctional aliphatic, alicyclic or aromatic compound containing achain extension segment connected to the cationic reactive group with amolecular weight of at least about 100 and not more than
 2000. 20. Acurable composition according to claim 1 wherein the compositioncontains about 4 to 30% by weight of a free radically curable componentcomprising at least 4% by weight one mono- or di(meth)acrylate and atleast 4% by weight a poly(meth)acrylate having (meth)acrylatefunctionality greater than or equal to
 3. 21. A method of producing acured product, in which a composition according to claim 1 is treatedwith actinic radiation.
 22. A method of producing a cured product, inwhich a composition according to claim 7 is treated with actinicradiation.
 23. A method for producing three-dimensional shaped articlescomprising: a) treating a radiation-curable composition according toclaim 1 with actinic radiation to form an at least partially cured layeron the surface of said composition within a surface region correspondingto a desired cross-sectional area of the three-dimensional article to beformed, b) covering the at least partially cured layer produced in stepa) with a new layer of said radiation-curable composition, and c)repeating steps a) and b) until an article having the desired shape isformed, and optionally, d) post-curing the resulting article.
 24. Amethod for producing three-dimensional shaped articles comprising: a)treating a radiation-curable composition according to claim 7 withactinic radiation to form an at least partially cured layer on thesurface of said composition within a surface region corresponding to adesired cross-sectional area of the three-dimensional article to beformed, b) covering the at least partially cured layer produced in stepa) with a new layer of said radiation-curable composition, and c)repeating steps a) and b) until an article having the desired shape isformed, and optionally, d) post-curing the resulting article.